Image coding and decoding method and apparatus considering human visual characteristics

Abstract

An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

What is claimed is: 
     
       1. An image decoding method comprising:
 obtaining a first quantization parameter for a first plurality of macroblocks from a bitstream, where the first plurality of macroblocks are not located on a boundary of a picture; 
 calculating a second quantization parameter for a second plurality of macroblocks in a predefined manner, where the second plurality of macroblocks are located on the boundary of the picture; 
 inverse-quantizing the first plurality of macroblocks of the picture using the first quantization parameter and the second plurality of macroblocks of the picture using the second quantization parameter, respectively; and 
 inverse-transforming the inverse-quantized first plurality of macroblocks and second plurality of macroblocks, 
 wherein the second quantization parameter is not obtained directly from the bitstream. 
 
     
     
       2. The method of  claim 1  further comprising adding an image restored for each macroblock according to corresponding positions. 
     
     
       3. The method of  claim 1 , wherein the second quantization parameter for the boundary of the picture is determined according to a predetermined rule. 
     
     
       4. The method of  claim 1 , wherein the second quantization parameter is obtained based on decoded information on the first quantization parameter for each macroblock, so that image quality is lowered in the boundary of the picture. 
     
     
       5. The method of  claim 1 , wherein the inverse-quantizing comprises inverse quantizing portions of the picture using the second quantization parameter varied based on the first quantization parameter of each macroblock. 
     
     
       6. The method of  claim 5 , wherein the second quantization parameter is determined according to a predetermined rule. 
     
     
       7. An image decoding method comprising:
 obtaining a first quantization parameter for a first plurality of macroblocks from a bitstream, where the first plurality of macroblocks are not located on a boundary of a picture; 
 calculating a second quantization parameter for a second plurality of macroblocks in a predefined manner, where the second plurality of macroblocks are located on the boundary of the picture; 
 inverse-quantizing the first plurality of macroblocks of the picture using the first quantization parameter and the second plurality of macroblocks of the picture using the second quantization parameter, respectively; and 
 inverse-transforming the inverse-quantized first plurality of macroblocks and second plurality of macroblocks, 
 wherein the second quantization parameter as it is, is not included in the bitstream. 
 
     
     
       8. The method of  claim 7  further comprising adding an image restored for each macroblock according to corresponding positions. 
     
     
       9. The method of  claim 7 , wherein the second quantization parameter for the boundary of the picture is determined according to a predetermined rule. 
     
     
       10. The method of  claim 7 , wherein the second quantization parameter is obtained based on decoded information on the first quantization parameter for each macroblock, so that image quality is lowered in the boundary of the picture. 
     
     
       11. The method of  claim 7 , wherein the inverse-quantizing comprises inverse quantizing portions of the picture using the second quantization parameter varied based on the first quantization parameter of each macroblock. 
     
     
       12. The method of  claim 11 , wherein the second quantization parameter is determined according to a predetermined rule. 
     
     
       13. An image decoding method comprising:
 obtaining a first quantization parameter for a first plurality of macroblocks from a bitstream, where the first plurality of macroblocks are not located on a boundary of a picture; 
 calculating a second quantization parameter for a second plurality of macroblocks in a predefined manner, where the second plurality of macroblocks are located on the boundary of the picture; 
 inverse-quantizing the first plurality of macroblocks of the picture using the first quantization parameter and the second plurality of macroblocks of the picture using the second quantization parameter, respectively; and 
 inverse-transforming the inverse-quantized first plurality of macroblocks and second plurality of macroblocks, 
 wherein the second quantization parameter is not obtained directly from the bitstream in which the second quantization parameter as it is, is not included. 
 
     
     
       14. The method of  claim 13  further comprising adding an image restored for each macroblock according to corresponding positions. 
     
     
       15. The method of  claim 13 , wherein the second quantization parameter for the boundary of the picture is determined according to a predetermined rule. 
     
     
       16. The method of  claim 13 , wherein the second quantization parameter is obtained based on decoded information on the first quantization parameter for each macroblock, so that image quality is lowered in the boundary of the picture. 
     
     
       17. The method of  claim 13 , wherein the inverse-quantizing comprises inverse quantizing portions of the picture using the second quantization parameter varied based on the first quantization parameter of each macroblock. 
     
     
       18. The method of  claim 17 , wherein the second quantization parameter is determined according to a predetermined rule.